1) Field of the Invention
The present invention relates to a speech input device that requires speech input such as recording equipment, a cellular phone terminal or a personal computer.
2) Description of the Related Art
In recent years, a data communication function for transmitting and receiving text data of about several hundred characters is often installed, as a standard equipment, into a portable terminal such as a cellular phone terminal or a personal handyphone system (PHS) terminal besides a telephone conversation function.
According to IMT-2000 (International Mobile Telecommunications-2000) that is a next-generation communication scheme, one portable terminal uses a plurality of lines, and it is thereby possible to perform data communication without disconnecting speech communication while the speech communication is being held. Accordingly, the portable terminal of this type may possibly be used in a case where text is input by operating keys during a telephone conversation and then data communication is also performed.
In recent years, an attention has been paid to an Internet Protocol (IP) telephone system that requires a less expensive call charge than that of an ordinary telephone call. This IP telephone system is referred to as an Internet telephone system. This is a communication system enabling a telephone conversation similarly to an ordinary telephone by exchanging speech data between IP telephone devices each of which is provided with a microphone and a loudspeaker.
The IP telephone device is a computer that enables network communication and is equipped with an e-mail transmitting/receiving function through the operation of a man-machine interface such as a keyboard and a mouse.
Meanwhile, as explained above, if a man-machine interface (keys, keyboard, mouse) is operated during a telephone conversation using a conventional portable terminal or an IP telephone device, then an operation sound (click sound or the like) which is regarded as noise is captured by the microphone, and superimposed on speech. Therefore, tone quality is disadvantageously, greatly deteriorated.
To solve this problem, it may be considered to employ a method of eliminating the component of the noise (operation sound) contained in speech signals that are input into the microphone by means of a noise elimination device. According to this method, however, the side of the noise elimination device cannot predict the occurrence of an operation sound, and therefore noise elimination processing always needs to be executed to the sound signal that is input into the microphone. With this method, therefore, the noise elimination processing is conducted to the sound signal even if no noise is present, unavoidably causing the deterioration of tone quality.